Biomedical subjects

J E Misner

Publications and source records attributed to J E Misner.

At least 19 recordsLinked to original sources

PubMed1998

Age-related variability in body composition methods for assessment of percent fat and fat-free mass in men aged 20-74 years.

INTRODUCTION: Assessing body composition is important because of the association between excess body fat or obesity and the increased risk for coronary artery disease, diabetes, hyperlipidaemia and hypertension. Methodological differences among indirect body composition techniques are a source of variability that can affect estimations of fat-free mass (FEM) or percent fat, especially for different age groups. PURPOSE: This study examined the effect of age on the estimation of body composition by three methods based on the two-component model. One hundred and fifty-three men were placed into 5-year age groups from 20-24 to 70-74 years. Body composition was assessed by hydrodensitometry (underwater weighing; 40K spectroscopy (K40) and anthropometry. RESULTS: Day-to-day reliability was excellent for each method. Correlation coefficients between methods, independent of age, ranged from r= 0.71 (K40 and UWW) to r = 0.83 (UWW and anthropometry) for% fat and from r = 0.76 (K40 and anthropometry) to r = 0.90 (UWW and anthropometry) for FFM. Correlations between techniques weakened and showed greater variability as age increased. UWW produced the highest % fat and lowest FFM for the different age groups, while K40 and anthropometry yielded similar body composition values. All three methods detected age-related differences in % fat; however, only UWW determined a significant age effect in FFM. The greatest discrepancies between the methods occurred for the oldest age groups (60-74 years), but noticeable differences began occurring after the age of 40. CONCLUSIONS: Each method produced reliable data. Care should be taken when choosing any method based on the two-component model, especially when different age groups are being examined, since estimating % fat and FFM is dependent on the age-related chemical composition of an individual and the limitations of each method.

Adiposity↗

PubMed1997

The effects of different thermal environments on the physiological and psychological responses of firefighters to a training drill.

Little is known about the impact of thermoregulatory demands on cardiovascular and psychological responses of firefighters during firefighting activities. This study examined selected responses to a training drill in different thermal environments. Male firefighters (n = 16) were randomly assigned to perform a simulated ceiling overhaul task for 16 min in either a neutral (13.7 degrees C) or hot (89.6 degrees C) condition while wearing standard firefighting turnout gear. Physiological and psychological measures were assessed before, after 8 min and 16 min of firefighting activity, and following a 10-min recovery period. The variables assessed included heart rate (HR), tympanic temperature (Ttymp), lactate level (LAC), blood glucose level, ratings of perceived exertion (RPE), perceptions of respiration, thermal sensations (TS) and state anxiety (SA). Significant increases were seen for HR, Ttymp, LAC, RPE and SA, with the increases being much greater following the hot condition. Recovery was significantly slower following work in the hot condition. These findings suggest that the addition of a live fire (a common situation for firefighters) contributes to increased cardiovascular and psychological strain at a standardized workload.

Adult↗

PubMed1996

Isometric intermittent endurance of four muscle groups in men aged 20-74 yr.

Muscular endurance of upper and lower extremities may provide a more practical measure of muscle function related to normal daily activity than measures of strength, especially with the elderly. Maximal isometric intermittent endurance of the finger flexors, thumb abductors, dorsiflexors, and plantar flexors were characterized by peak force, impulse, percent total impulse, and percent force decrement in men aged 20-74 yr. Volunteers (N = 153) were placed into appropriate 5-yr age groups: 20-24, 25-29, ..., 70-74 yr. The intermittent endurance task consisted of 11 consecutive, 2-s maximal contractions, each separated by 3-s rest. Age group differences within each 2-s interval as well as differences in endurance were determined by ANOVA, and after adjusting for differences in body composition, by ANCOVA. The lower extremities had the greatest declines in absolute measures of force within each 2-s interval, and declines occurred earlier than previously reported. When values were expressed as percent change over the entire endurance task, there was generally no age group difference in force or impulse; however, there were significant muscle group differences. In conclusion, declines in absolute measures of force occurred at different ages depending on the muscle group; however, relative measures of muscular endurance were maintained for all age groups but varied by muscle group location.

Adult↗

PubMed1996

Physiological, psychophysical, and psychological responses of firefighters to firefighting training drills.

This study was designed to describe the physiological, psychophysical, and psychological responses of firefighters to firefighting drills in a training structure containing live fires. Fifteen male firefighters, wearing standard turnout gear which resulted in full encapsulation, performed two firefighting tasks (advancing fire hose, chopping wood) while inside the training structure. Measurements of heart rate, tympanic membrane temperature, blood lactate, perceptions of respiration, mood, perceived exertion, and thermal sensation were obtained after 8 min of advancing fire hose, and again after 8 min of chopping. Heart rate and temperature increased significantly from baseline and from advancing hose to wood chopping, whereas blood lactate increased initially after advancing the hose and remained elevated at the end of the chopping task. At the completion of the test (both tasks), mean heart rate (182.3 b.min-1), temperature (40.1 degrees C, [104.1 degrees F]), and blood lactate (3.8 mMol) suggested that the firefighting tasks used in this study impose considerable physiological strain on firefighters. Psychophysical and psychological data mirrored the greater physiological strain following firefighting tasks performed in a hot environment while wearing full turnout gear.

Adult↗

PubMed1995

Age-related patterns in body composition for men aged 20-79 yr.

Fat-free body mass has been reported to decline by 30% between the ages of 30 and 70 yr, whereas body weight increases until age 50 yr. This study examined the age-related patterns in body composition, specifically its two components, fat-free body mass and fat mass, in 157 men aged 20-79 yr. Total body composition was assessed by hydrodensitometry and subcutaneous fat was measured with skinfolds. Approximately 15 men were tested in each of the 12 5-yr age groups (20-24, 25-29, 30-34, ... 75-79 yr). Body density, as determined by underwater weighing, was lower successively from the youngest to oldest age groups; men below age 40 yr had significantly higher (P < 0.01) body densities than the older men. Although there was a gradual decline in fat-free body mass with increasing age, there was not a significant age group effect until age 70 yr. Fat mass gradually increased with increasing age; men above age 40 yr had significantly higher (P < 0.01) total body fat when compared to the younger men. Subcutaneous body fat was similar at the distal limb locations for each age group; however, the proximal trunk locations, especially the abdomen, demonstrated significantly (P < 0.01) higher skinfold thicknesses with increasing age. In conclusion, fat-free body mass was maintained to a later age than previously reported; thus, the age-related decline in body density could be attributed to an age-related increase in body fat.

Adipose Tissue↗

PubMed1993

Cardiovascular responses to sustained maximal isometric contractions of the finger flexors.

This study investigated cardiovascular responses to 2 min sustained submaximal (20% MVC) and maximal (100% MVC) voluntary isometric contractions of the finger flexors in healthy young women. Cardiovascular variables investigated were: heart rate (fc), mean arterial pressure (Pa), and stroke volume (SV). Doppler echocardiography was used to estimate SV from measures of aortic diameter (AD) and time-velocity integrals. Preliminary studies indicated that AD did not change significantly after 2 min sustained 100% MVC. Therefore, pre-exercise AD values were used to calculate SV before, during and after exercise. During the 2-min 100% MVC period, fc and Pa increased significantly during the first 30 s of contraction. fc then remained constant during the remainder of the 2-min contraction period, while Pa continued to rise. SV did not change significantly during the 100% MVC task but increased significantly during recovery from sustained 100% MVC. The data suggest that the magnitude of cardiovascular responses to isometric exercise is dependent on the specific task performed, and that there is a different pattern of response for fc, Pa, and SV during 20% and 100% MVC tasks. Unlike fc and Pa, SV did not change significantly during isometric exercise, but increased significantly after sustained 100% MVC.

Adult↗

PubMed1993

Failure to find increased TEM at rest and during exercise in aerobically trained and resistance trained subjects.

This study examined the metabolic response to a 763-kcal mixed meal at rest and during 30 min of exercise at 50% maximal oxygen consumption (VO2max) in 8 aerobically trained (AT), 8 resistance trained (RT), and 8 untrained (UT) subjects. Oxygen consumption (VO2) was measured minute by minute during 30 min of exercise by indirect calorimetry on 2 nonconsecutive days (postabsorptive exercise, PA; and postprandial exercise, PP). Total VO2 consumed and total caloric expenditure during the PA and PP conditions were similar for the three groups, indicating that prior food intake did not affect energy expenditure during exercise. Consequently, TEM during exercise did not differ significantly among the groups. Respiratory exchange ratio (R) differed significantly only during the PA condition, with the AT group exhibiting significantly lower R values compared to the RT group, and significantly lower R values compared to the UT group. These data suggest that the consumption of a meal 30 min prior to exercise does not increase TEM during exercise in AT, RT, and UT subjects.

Adolescent↗

PubMed1992

Cortisol levels during prolonged exercise: the influence of menstrual phase and menstrual status.

The purpose of this study was to determine the influence of menstrual phase and menstrual status on the cortisol response during 90 minutes of treadmill running at 60% VO2max. Eight eumenhorrheic athletes were tested in the early follicular (EF) (day 3-5), late follicular (LF) (day 13-15) and mid-luteal (ML) (day 22-24) phases. Six amenorrheic athletes were tested on two separate occasions. The resting cortisol levels were similar in each menstrual phase and overall a decreasing pattern of cortisol response to exercise was observed in all menstrual phases (P greater than .05). The amenorrheic athletes had a significantly greater (P less than .01) pattern of cortisol response than was observed in eumenorrheic athletes. The net increment in cortisol levels during exercise were distinctly greater (P less than .01) in amenorrheic than eumenorrheic athletes (amenorrheic: 413.8 +/- 113.1, eumenorrheic: EF: -482.8 +/- 88.3, LF: -311.8 +/- 102.1, ML: -386.3 +/- 146.2 nmol.l-1). In conclusion the cortisol levels are independent of menstrual phase. Also a larger cortisol increment is observed in amenorrheic athletes in response to prolonged submaximal exercise. The elevated cortisol levels in amenorrheics at rest and throughout exercise provides further evidence that disturbances in the hypothalamic-pituitary-adrenal function are associated with exercise-induced amenorrhea, although the site(s) of physiological disturbance have not been identified.

Adult↗

PubMed1992

Interactive videodisc calorimetry simulations for exercise physiology laboratories.

Six interactive videodisc lessons for college-level exercise physiology classes were developed. The six lessons were written using TenCore for the IBM M-Motion technology. The focus of the laboratories is on exercise metabolism measured by indirect calorimetry. The six lessons are as follows. 1) Environmental measures: determines whether conditions are favorable for exercise. Dry bulb, wet bulb, and black globe temperatures are obtained to calculate relative humidity, STPD gas volumes, and the wet bulb-globe temperature index. 2) Basal metabolism: emphasizes the mechanics of calculating energy expenditure through indirect calorimetry. Lying, sitting, and exercise metabolism are compared. 3) Submaximal metabolism: compares the energy cost of walking a mile and running a mile. Steady-state exercise, oxygen debt, and oxygen deficit are explored. 4) Maximal metabolism: assesses maximal oxygen consumption using the Bruce protocol. 5) Hormonal responses to prolonged exercise: demonstrates the effect of hormonal levels on %fat and %carbohydrate utilization during 1 h of exercise. 6) Metabolic responses to supramaximal exercise: estimates anaerobic power using the Wingate test.

Calorimetry↗

PubMed1992

The relative contribution of strength and physique to running and jumping performance of boys 7-11.

The purpose of this study was to determine the association of static strength with motor performance of 7 through 11 year old boys (N = 60) after accounting for differences in physique, i.e., body size, shape, and composition. Static strength measures included thigh extension, leg extension and plantar flexion measured by electronic transducer and back lift, leg lift, and right and left grips measured by spring dynamometer. Measures of body composition consisted of fat estimated from triceps, subscapsular and calf skinfolds, and fat-free body weight estimated from potassium-40 measurements. Body structure consisted of skeletal widths, and segment girths, lengths and volumes. The dependent variables were vertical jump, standing broad jump, 50-yard dash, 600-yard run and mile run. The measures of strength increased the variance accounted for from 10 to 23% over that when body size, composition and structure were used without strength. An exception was vertical jump where no increase in the variance accounted for was found with the addition of strength variables. The regression equations determined for the sample of 60 boys rendered multiple R's ranging from 0.64 (mile run) to 0.75 (50-yard dash). It was concluded that strength has a significant relation to motor performance and that its contribution can be better assessed after accounting for differences in body size, shape, and composition.

Anthropometry↗

PubMed1992

Substrate oxidation and GH responses to exercise are independent of menstrual phase and status.

The purpose of this study was to determine the extent to which growth hormone (GH) and energy substrate utilization are influenced by basal sex steroid levels during prolonged submaximal exercise across menstrual phase and status. Also the 17 beta-estradiol (E2) and progesterone responses during prolonged exercise were compared according to menstrual phase and menstrual status. Six amenorrheic (AMc) athletes and seven eumenorrheic (EUc) athletes ran at 60% VO2max for 90 min and serial blood samples were taken at rest, every 10 min throughout exercise, and 5 and 15 min post-exercise. The EUc athletes were tested in the early follicular phase (EF) (days 3-5), the late follicular phase (LF) (days 14-16) and the mid-luteal phase (ML) (days 22-25). The incremental GH response to exercise, measured by area under the curve, was consistent with previous reposts and was not altered according to menstrual phase or status (EF-37.5 +/- 11.5, LF-61.9 +/- 11.5, ML-48.1 +/- 12.8 micrograms.1-1.90 min-1). Furthermore, carbohydrate and fat utilization during exercise were not influenced by basal sex steroid levels associated with menstrual phase or status. The incremental E2 response to exercise in AMc athletes was significantly smaller than seen in EUc athletes (AMc-208.1 +/- 44.0, EF-383.0 +/- 116.4, LF-204.7 +/- 84.1, ML-45.1 +/- 18.4 pmol.1(-1).90 min-1), although the pattern of release is similar between groups. In conclusion, GH levels and substrate utilization are independent of both menstrual phase and status; hence, menstrual phase has no negative ramifications on metabolism during exercise. Amenorrhea does not result in metabolic consequences during prolonged exercise by influencing substrate utilization.

Adolescent↗

PubMed1992

Effects of oral contraceptives on hormonal and metabolic responses during exercise.

This study examined the influence of oral contraceptives (OC) on GH and PRL responses and on energy substrate utilization during prolonged submaximal exercise in moderately active women (21-30 yr). Eight women taking OC (OC) and eight women with normal menstrual cycles (C) performed a standardized treadmill test of 90 min at 50% maximal oxygen uptake. Blood samples were withdrawn from an indwelling venous catheter during a 2-h rest period, at 10-min intervals during exercise and at 3 and 15 min of recovery. Serum concentrations of glucose, GH, PRL, E2, and P4 were assayed. Carbohydrate and fat utilization were estimated from respiratory exchange ratios. Basal serum levels of GH, PRL, and glucose were not significantly different (P greater than 0.05) between OC and C. OC had significantly higher (P less than 0.05) serum GH levels than C at 10 and 20 min of exercise, but the integrated areas for GH responses were not different (P = 0.059). Serum PRL levels significantly decreased (P less than 0.05) during exercise, and PRL responses were similar for the two groups. OC exhibited significantly lower blood glucose levels (P less than 0.05) during exercise and utilized significantly lower total grams of carbohydrate (P less than 0.05) during exercise than C. In conclusion, OC use was associated with enhanced GH responses, lower glucose levels, and diminished carbohydrate utilization during prolonged exercise. These results indicated that OC users demonstrated a greater carbohydrate-sparing ability than eumenorrheic women, which may be related to the contra-insulin effects of GH. The lower blood glucose levels, however, suggest the sparing of carbohydrate may act to compensate for decreased hepatic glucose output, similar to animal data.

Adult↗

PubMed1991

Isometric muscle force production as a function of age in healthy 20- to 74-yr-old men.

Typically, previous studies have focused on one muscle group, the finger flexors, and only one aspect of muscle function, strength, when assessing age-related muscle force production characteristics. In the present study, the maximal voluntary isometric contraction force-time curves of five muscle groups (right hand finger flexors, right thumb abductors, right forearm extensors, right leg dorsiflexors, and right leg plantar flexors) were assessed in men, ranging in age from 20 to 74 yr. One hundred fifty-three volunteers were placed into appropriate 5-yr age groups: 20-24 (N = 14), 25-29 (N = 15), 30-34 (N = 16), 35-39 (N = 13), 40-44 (N = 16), 45-49 (N = 11), 50-54 (N = 16), 55-59 (N = 12), 60-64 (N = 17), 65-69 (N = 13), and 70-74 (N = 10) years. Muscle function was characterized by a number of force-time parameters, including strength, time, rate, and impulse. The data were analyzed both with and without consideration of the influence of physique and body composition. The results indicated that there were significant age group differences in the ability to produce maximal force (strength) (P less than 0.05), to generate maximal rates of force production (P less than 0.05), and in the total forces generated (impulse) (P less than 0.05), with an overall and in the total forces generated (impulse) (P less than 0.05), with an overall decline with increasing age.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Lower thermic effect of a meal post-exercise in aerobically trained and resistance-trained subjects.

Despite the abundance of literature concerning the thermic effect of a test meal (TEM) at rest in trained and untrained subjects, there is little information available concerning the TEM post-exercise. Therefore, it was the purpose of this study to examine the metabolic response to a 763-kcal meal prior to 30 min of exercise at 50% VO2max, in aerobically trained (AT, N = 8), resistance-trained (RT, N = 8), and untrained (UT, N = 8) subjects. Mean (+/- SEM) VO2max was 60.7 +/- 2.3 ml.kg-1.min-1, 52.9 +/- 2.2 ml.kg-1.min-1 and 51.1 +/- 2.2 ml.kg-1.min-1, for the AT, RT, and UT groups, respectively. Mean (+/- SEM) percent fat was 13.7 +/- 1.2, 12.7 +/- 1.9, and 16.9 +/- 1.4 for the AT, RT, and UT groups, respectively. Post-exercise VO2 was measured by indirect calorimetry every half hour, on two nonconsecutive days (post-absorptive (PA) post-exercise and post-prandial (PP) post-exercise) for 3 h. The total TEM (post-exercise PP VO2 minus post-exercise PA VO2) was 4.86 +/- 1.62, 5.22 +/- 1.80, and 9.36 +/- 5.08 I for the AT, RT, and UT groups, respectively. The TEM post-exercise was significantly lower (P less than 0.05) for the AT and RT groups compared with the UT group. Respiratory exchange ratio (R) differed significantly only during the PA post-exercise condition, with the AT group exhibiting significantly lower (P less than 0.01) values compared with the RT and UT groups. PA post-exercise R for the RT group was not significantly different (P = 0.09) from the UT group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1990

Sex differences in static strength and fatigability in three different muscle groups.

Maximal voluntary static muscle force production was assessed both in strength trials and during 2-min contractions by three muscle groups (right-hand finger flexors [RHF], right-leg extensors [RLE], and both leg extensors [BLE]) in young males (n = 13) and females (n = 14). There was a significant difference (p less than .01) between males and females for RHF strength and BLE strength but no significant difference between sexes for RLE strength. During the 2-min task, impulse (force x time) declined significantly (p less than .001) and there was a significant difference (p less than .001) between muscle groups, but there was no difference between sexes. There was a significant (p less than .05) sex x time interaction for the impulse values indicating that the fatigability was greater in males than females.

Adolescent↗

PubMed1990

Cardiovascular response to sustained maximal voluntary static muscle contraction.

The cardiovascular response to maximal, voluntary, sustained 2-min static contraction by three different muscle groups (right hand finger flexors [RHF], right leg extensors [RLE], and both leg extensors [BLE]) was studied in young adult males (N = 13) and females (N = 14). Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were recorded at 30 s intervals prior to, during, and after exercise. Mean arterial blood pressure (MABP) and pulse pressure (PP) were computed from SBP and DBP. The force of muscle contraction was monitored continuously throughout the 2-min task. Data were analyzed by MANOVA. The results showed that impulse (force x time) declined significantly throughout exercise, and there were significant differences in impulse among muscle groups. SBP, DBP, PP, and MABP increased significantly throughout the 2-min contraction period, while heart rate increased initially and then leveled off. The magnitudes of the blood pressure and HR responses were related to the muscles involved: BLE greater than RLE greater than RHF. Blood pressures during rest and exercise were significantly lower for females than for males, but there was no sex effect for heart rate. These findings suggest that blood pressure increases throughout sustained static muscular contractions despite significant reductions in force production. Heart rate, on the other hand, does not increase throughout exercise under these conditions. It appears that heart rate and blood pressure responses to sustained static contraction are mediated by different mechanisms, but these mechanisms are similar for males and females.

Adolescent↗

PubMed1989

Development of placement tests for firefighting: a long-term analysis by race and sex.

This study summarises 16 years of data on simulated firefighting tasks used to select firefighters in the City of Chicago, Illinois. Four issues related to firefighter applicant testing are analysed: (1) test reliability; (2) test specificity; (3) racial/ethnic aspects of performance; and (4) sex-related aspects of performance. The findings indicated that the tests were moderately reliable but considerable day-to-day improvement was observed particularly among females. With respect to test specificity, simulated firefighter tasks do not appear to be highly correlated to traditional physical performance tests. Little difference was observed between the black, white and hispanic subjects tested. There were large differences between males and females on the physical performance tests and this difference appeared to be, in part, due to differences in size and body composition between sexes. This finding was consistent with other studies.

Journal Article↗

PubMed1989

Age as a factor in the hemodynamic responses to isometric exercise.

This study was designed to determine the effect of isometric contractions of the finger flexors and leg extensor muscle groups on the cardiovascular responses of men 18-31 and 50-71 years of age. A 2X2X4 split-plot design was carried out with men representing two age groups, using two muscle groups and performing isometric contractions at four different intensities. Analysis of variance indicated significant differences for all main effects. The systolic and diastolic blood pressures were found to be (1) higher for the leg extension contractions compared to the finger flexion contractions, (2) higher for each increment in %MVC workload, and (3) higher for the older individuals. Heart rate responses were found to be (1) higher for the leg extension exercises, (2) higher with each increase in %MVC, and (3) higher for the younger subjects. Stroke volumes demonstrated (1) higher values for the young men at each workload, (2) lower values for leg extension exercises, and (3) a greater decline with longer contraction times. The older individuals had higher pressor responses than did the younger subjects, higher pressor and heart rate responses were observed with isometric leg extension exercises and increasing %MVC levels, and the older subjects had lower stroke volume responses compared to the younger subjects.

Adolescent↗